What are the various methods of research used in psychology?

When applicable, the experimental method is preferred for studying problems because it seeks to control all variables except the ones being studied. The independent variable is the one manipulated by the experimenter; the dependent variable (usually some measure of the subject’s behavior) is the one being studied to determine if it is affected by changes in the independent variable. In a simple experimental design, the experimenter manipulates one independent variable and observes its effect on one dependent variable and observes its effect on one dependent variable.

In many experiments, the independent variable is something that is either present or absent. The simplest experimental design includes an experimental group ( with the condition present for one group of subjects) and a control group ( with the condition absent for another group of subjects). If the difference in means between the experimental and the control group is statistically significant, we know that the experimental condition had a reliable effect; that is, the difference is due to the independent variable, not to chance factors or a few extreme cases.

If an investigator has no control over which conditions, a correlational method may be used.

This method determines whether a naturally occurring difference is associated with another difference of interest. The degree of correlation between two variables is measured by the correlation coefficient, r. It is a number between 0 and ; a perfect relationship is indicated by 1. As r goes from 0 to 1, the strength of the relationship increases. The correlation coefficient can be positive or negative, depending on whether one variable increases with another (+) or one variable decreases as the other increases (-).

Why does a correlation coefficient not indicate a cause and effect relationship? Because a third variable, an intervening variable, often accounts for the relationship between two variables. Take the example of ten used by psychologist David Schroeder: Suppose there is a correlation of +.80 between the number of ice cream cones sold during August in New York and the number of babies that die during August in India. Does eating ice cream kill babies in another nation? No, that would not make sense. Instead, we look for the third variable that would explain our high correlation. In this case, the answer is clearly the summer heat.

Another approach to research is the observational method, in which one observes the phenomenon of interest. Researchers must be trained to observe and record accurately to avoid projecting their own biases into what they report. Phenomena that are difficult to observe directly may be observed indirectly by survey (questionnaires and interviews) or by reconstructing a case history. Most case histories are prepared by reconstructing the biography of a person on the basis of remembered events and records.